1. Field of the Invention
This invention relates to a process for preparing novel synthetic fibers which are non-flammable and have excellent dyeability, heat resistance and mechanical properties. Particularly, it relates to a process for preparing novel synthetic fibers which comprise a vinyl chloride resin component and an acrylonitrile resin component, by way of matrix polymerization and/or blending.
2. Description of the Prior Art
Poly(vinyl chloride) fibers are widely employed for commercial uses because of their low-cost and excellent properties for the synthetic fibers. However, the PVC fibers can not be used in the presence of heat or in hot water, since the fibers are poor in resistance to heat and hot water. The acrylic fibers are consumed in a large quantity owing to their desirable properties such as excellent dyeability, feeling similar to wool and higher bulkiness. The cost of acrylic fibers is rather high in comparison with PVC fibers, and, furthermore, acrylic fibers are poor in antiflaming property.
Although PVC fibers are the synthetic fibers of low cost which have many valuable properties, and the flame-resistance thereof is unique among many synthetic fibers, they have a serious defect in that they begin thermal shrinkage even at 80.degree. - 100.degree. C. In order to eliminate this defect, the following treatments have been tried.
(I) A method of grafting acrylonitrile on PVC fibers: The percent graft of acrylonitrile must be as much as 100% based on the weight of PVC fibers for increasing the resistance to heat. In this method, their tenacity per denier decreases, since the grafted acrylonitrile polymer contributes little to their strength but increases their weight.
(II) A method of copolymerizing vinyl chloride and acrylonitrile: No satisfactory heat-resistant fibers have so far been obtained, when compared with nylon, polyester, acrylics, vinylon and the like.
(III) A method of blending PVC and another polymer resistant to heat: By this method, it is very difficult to obtain a completely homogeneous blend of two species of polymers. For example, some binary mixtures of polymers will dissolve in a common solvent through intense agitation and may appear to be a homogeneous solution. However, such a solution generally separates into two phases when the solution is left to stand for a long period of time.